injection volume validation

[sirus]

Hello,
Can anyone please help me how to validate the injection volume of the autosampler? Simply, I want to find out if the LC autosampler is injecting the specified volume or not?

Any literature, protocol, info are highly appreciated? Also if anyone can share a protocol or literature for building calibration curve that will be great.

Begineer to LC-MS.

Thank you.

Sirus

[tkubowicz]

Hello

For typical OQPV procedure for LC you have:
1.injection precision test - 5 injections of std to check RSD
2.injection linearity (additional test) - Any choice of 5 injection volumes. Constant concentration standard could be 5 ug/ml caffeine.

If you want to check if correct volume is injected you can weight vial before and after injection and calculate injected volume - assuming that 1g of water is 1 ml.

Regards

Tomasz Kubowicz

[DR]

@Tomasz Kubowicz

Actually, this method (weighing vial before and after making injections) makes sense but is not practical unless your equipment meets a number of assumptions; chief among them being:
*that you have a balance that can accurately weigh mg quantities while having >2g on the pan
*that your LC withdraws no more than what will be injected

While there are balances that can do this job, there tend to be few or no older ones that can do it accurately enough to validate to any commonly accepted compendial standard.

There are autosamplers that do not waste any sample, but not typically from the larger vendors. Some Shimadzu autosamplers that include the needle in the high pressure portion of the flow path do not waste any sample.

[tkubowicz]

Hello

I was clear that this method (weighing) is only to check if correct volume is taken. I wouldn't even consider to validate something as "injection volume".
As far as I know typical OQ/PVprotocols includes: injection precision test and additional (if someone wants) injection linearity test.
The only test I can think of is for example Waters separation module with 8 syringes for dissolution bath - then you need to weight vials before and after to check if correct volume is delivered.

Regards

Tomasz Kubowicz

[sirus]

Thank you all for your nice suggestions.

Sirus